1. Field of the invention
The present invention relates in general to magnetrons. Note particularly, the present invention relates to apparatus for cooling the magnetron of which cooling fins are provided, in order to improve the cooling effect of the magnetron, with a plurality of protruded and depressed embossments individually.
2. Description of the Prior Art
As well known to those skilled in the art, known microwave ovens or similar heating systems are generally provided with individual magnetrons for generating microwave. In order to cool the magnetron, the microwave oven also includes forced air-cooled type cooling apparatus of which a plurality of cooling fins are mounted on the outer surface of an anode of the magnetron.
With reference to FIG. 1 showing a representative embodiment of the known magnetron suitable used for microwave ovens, the magnetron includes an anode 1 for generating microwave as well as high temperature heat. The microwave generated by the anode 1 is in turn outputted from an microwave output part 5. Above and below the anode 1, upper and lower permanent magnets 6 are arranged in order to form a magnetic field in the magnetron. Here, the high temperature heat of the anode 1 may cause the magnetron to be heated and, as a result, to be troubled. Thus, the magnetron further includes known cooling apparatus for removing the high temperature heat of the anode 1. This known cooling apparatus comprises a plurality of stepped cooling fins 2 which are mounted on the outer surface of the anode 1 in order to provide enlarged cooling surface for radiating the heat of the anode 1 therefrom. This known cooling apparatus further includes a yoke 3 for guiding the cooling air to the inside of the magnetron and a fan blower 4 for forcedly sending the cooling air to the inside of the magnetron.
In the above magnetron, when the resonator of the magnetron, i.e., the anode 1 is applied with an electric current having a predetermined oscillation frequency, the anode 1 emits thermions and, as a result, generates microwave of which a part is in turn applied to the microwave output part 5 to be outputted therefrom and the other in the form of thermal loss of the anode 1 is transmitted to the outside of the anode 1. Here, the high temperature heat, i.e., the thermal loss of the anode 1 is first transmitted to the outer surface of the anode 1, and thereafter, radiated to the outside of the magnetron through the plurality of cooling fins 2 mounted on the outer surface of the anode 1. At this time, the cooling air which is sent to the inside of magnetron by the fan blower 4 is circulated in the magnetron in such manner that it passes through the spaces between the yoke 3 and the cooling fins 2 as well as the spaces between adjacent fins 2. In this respect, the known cooling apparatus of the magnetron prevents overheat of the anode 1 and, as a result, deterioration of the permanent magnets 6 caused by the overheat of the anode 1.
However, the known cooling apparatus has a pressure difference between the side and the rear of the anode 1 as depicted in FIG. 2, thereby causing the cooling air passing between the adjacent cooling fins 3 to be forced outwards from the rear of the anode 1. In this regard, the cooling airflow E is deflected from its desired flow direction and this causes separation of the airflow E from the rear surface of the anode 1.
Such a separation causes deficient contact of the cooling air with the rear surface of the anode 1 and, as a result, prevents the rear surface of the anode from being sufficiently cooled by the cooling air. Therefore, a separation region is inevitably formed on the rear surface of the anode 1. In this regard, there is a temperature difference of about several .degree.C. to several ten .degree.C. between the front surface and the rear surface of the anode 1. This temperature difference causes the anode 1 to be thermally deformed and, as a result, reduces the using life of the magnetron.
In addition, the cooling fins, while increasing the amount of cooling air circulation since the cooling air can smoothly pass by them thanking for their flat shapes, nevertheless reduces the relative friction of the cooling air with respect to them. In this regard, it is required to increase the friction between the cooling air and the cooling fins 2 in order to improve the cooling effect of the magnetron within an extent capable of maintaining a predetermined conductance.